Most IT departments in today's corporate world face growing user demands and shrinking budgets. Thus, storage vendors desire to develop cost efficient low-end systems with value-added features and availability levels typically found usually in enterprise class facilities. An exemplary system may be a serial attached SCSI (SAS) system.
SAS was developed as the evolutionary replacement for parallel SCSI (SCSI capable of supporting Serial ATA). SAS was envisioned to become the universal interconnect technology for mid-range and enterprise storage systems supporting multiple applications and deployment models and negating the need for multiple incompatible storage infrastructures. SAS provides high-end enterprise features (such as Fibre Channel, or the like), as well as the ability to support low-end desktop type storage media devices (such as Serial ATA, or the like).
Each SAS device contains one or more ports which may be a narrow port or a wide port. A wide port is created when there is more than one PHY in the port. A narrow port is created when there is only one PHY in the port. A PHY is a transceiver that electrically interfaces with a physical link combined with the portions of the protocol that encodes data and manages the reset sequences. Generally, PHYs are preconfigured to corresponding ports and do not change when different width port devices or expanders have been attached. Pre-configuration of ports does not allow for a flexible generic design and requires external controller intervention to reconfigure the PHYs to match the attached SAS end device or the attached expander.
Therefore, it would be desirable to provide a method to dynamically configure SAS PHYs to match the attached device port width.